Heating device for glass lehrs and the like



June 13, 1939. L, P. PIAZZOLI. JR 2,162,030

HEA'IING DEVICE FOR GLASS LEHRS AND THE LIKE Original Filed April 21,1930 3 s t s 1 June 13, 1939.

| P. JPIAZZOLI. JR

HEATING DEVICE FOR GLASS LEHRS AND THE LIKE 2 SheetsSheet 2 OriginalFiled April 21, 1930 pxugyfn waw-ron adapted to create a substantiallyuniform tem- Patented 13, 1939 UNITED STATES PATENT OFFICE HEATINGDEVICE FOR GLASS LEHRS AND THE LIKE Louis P. Pianoli, Jr.. Connellsville, PL, a-ignor to Capsta'n Glass Company, Oonnellsville, Pa.. 7 acorporation of Delaware Original application April 21, 1930, Serial No.445,886. Divided and this application'luly 3, 1936, Serial No. 88,748 I6Claims.

The present application is a division of the application of Louis P.Piazzoli, Jr., Serial No.

445,886, now Patent No. 2,056,207, dated October- 6, 1936, for Annealinglehr, and the invention relized for raising the temperature of the wareto the desired extent. Thereafter, the ware is permitted to coolgradually to prevent the establishment of strains as a result of thecooling operation. It is important that the heating-units be peraturetransversely of the lehr and a temperature gradient longitudinally ofthe lehr, increasing to a maximum and decreasing to normal temperatures.The problem of heating is oomphcated by reason of possible drafts in thelehr and by reason of the circulation of the heated air currentstransversely of the lehr, as well as by the effect of externalatmospheric temperatures which are minimized to a substantial extent butnot completely eliminated by insulation. Heating units known heretoforefor this pu p se have been unsatisfactory.

The present invention aims to overcome the difficul ties encounteredheretofore by creating air currentseif'ective primarily transversely ofthe lehr to create uniform heating conditions. These objects areachieved, in part, by creating heated air currents which rise along thesides of the lehr together and produce a uniform heating mediumtransversely of a lehr or furnace.

Another object of the invention is to provide a heating unit havinggreater heating capacity per unit of length at the ends thereof than atthe middle to create stronger heating currents at the ends adapted torise to the top of the lehr and be deflected downwardly into the weakerheating lates to the heating devices illustrated and de-' a continuousconveyor and heating units are uti-' An object of the present inventionisto provide currents at the middle of the lehr to form a uniformheating medium transversely thereof.

Another object of the invention is to provide a heating unit with adeflector adapted to direct heating currents of greatest intensityupwardly at the ends of the heating units and at the sides of the lehrto cause the currents to rise up and be deflected into the middle of thelehr to create uniform temperatures transversely thereof.

Another object of the invention is to provide heating units or devicesparticularly adapted for heating glass annealing lehrs.

Another object of the invention is to provide an improved heating unitfor lehrs and the like which is simple in construction, easy tomanufacture, and readily removed and replaced. L

Other and further objects of the invention will be obvious upon anunderstanding of the illustrative embodiment about to be described, orwill one skilled in the art upon employment of the invention inpractice.

A-preferi-ed embodiment of the invention .has been chosen for purposesof illustration and description and is shown in the accompanyingdrawings, forming a part of the specification,

wherein Fig. 1 is a perspective view illustrating a preferred embodimentof the present invention with part of the shield broken away;

Fig-2 is a fragmentary top plan view illustrating another embodiment ofthe invention;

Fig. 3 is a side elevational view, partly in section, illustratinganotherembodiilunt of the invention;

Pig. 4 is a sectional view taken H of Fig. 3;

Fig. 5- is .a side elevational view, partly in section, illustratingstill another embodiment of the invention; and l Fig. 6 is a sectionalview illustrating a heating unit mounted in an annealing-lehr, thearrows indicating the circulation of heat within the lehr. 1

Referring to the drawings, and more particularly to Fig. 1, thereisshown a base, frame or supporting structure-i having a resistanceelement 2 molmted thereon. The frame preferably is constructed of a pairof bars I held together by transversely extending bolts or rods 5 havinginsul'ators 6 mounted thereon for spacing 'the bars apart. Theinsulators have notches or grooves I at the top thereofwhich extendlengthwise with respect to the frame and are adapted to receive alongthe line to a suitable terminal for supplying electric cur-.

rent. The ribbon preferably is of uniform width and thickness throughoutits length and is bent" upon itself into a series of relatively shortloops 9 extending lengthwise with respectto the frame.

I Preferably, two rods having insulators thereon are utilized forsupporting each group of loops and seven groups or series of loops maybe utilized. Each group of loops may be held downwardly on the insulator6 by one or more tubular insulating members I mounted on a bolt H or thelike extending through upright members I! preferably,

secured to the bars 4 of the frame. The tubular insulatingr'nembers l0engage the resistance elements. lightly and are rotatable to permitthermal expansion and contraction of the resist-- ance element withoutstraining the supporting structure.

The loops may be of anydes'ired shape but,

are rounded at their ends to eliminate sharp corners. They arepreferably relatively short to reduce the amount of thermal expansion ofthe resistance element per unit of length and further minimize strainson the supporting frame.

The heating units described above are particularly adapted for heatingelectric annealing lehrs. and are designed to extend cross-wise ortransversely with respect to the lehr tunnel (Fig.

6). They are constructed to produce heating currents adapted to supplythe same amount of heat to the ware being annealed throughout the widthof the lehr tunnel, regardless of drafts or other adverse conditionswithin the lehr. This 45. result may be attained by providing the groupsof loops l4 adjacent the ends of the frame'with a greater number ofloops than the groups of loops 15 at the middle of the frame. Forexample, the groups l4 may have twice as many loops as thegroups l5.Hence, the length of the ,resistance element in groups I4 is twice thelength of element in groups l5 whereby twice as much heat is produced atthe ends of the supporting structure as at the middle. In some cases, itmay be suflicient to have less differences in the heating capacity ofthe groups, a

Preferably, the loops of groups l4 and I5 are of uniform length tosimplify the construction but, if desired, may be of different lengths.Also, certain loops may be spaced farther apart'than others to decreasethe intensity of the heatfor a given area. This is particularlyadvantageous because each unit is designed. to heat a longitudinalsection of the lehr. By spreading the loops apart at portions where lessheat is to be sup plied,.the heat nevertheless is distributed uniformly.l v

In Fig. 2, a slightly different construction is shown, wherein the samenumber of loops is provided in all-the groups but the thickness of theribbon is reduced at theends of the unit to increase the reslstance andproduce a greater amount of heat. This resistance element may be formedof an integral strip having its' thicknes'sreduced at the ends thennit'u' may be the lehr than at the middle.

its length, thus facilitating mounting the element 1 on the insulatingmembers 6. The loops preferably are of uniform length and widththroughout to distribute the heat uniformly.

In Figs. 3 and 4, another construction is shown wherein a heating uniteither like the unit shown in Fig, l or in Fig. 2 is utilized and ashield I6 is extended above the unit along the length thereof. Theshield preferably is formed of a metal which is a good conductor of heatand has a top portion l1 ad depending side flange I8 which are adaptedto be connected to the heating unit frame I in any suitable manner. Theshield prevents direct radiation'of heat from the heating strip and isadapted to radiate or distribute the heat throughout the width of thelehr. This provides a larger heat radiating surface, which permits moreeven radiation. Changes in temperature of the heating strip are,therefore,-transmitted very slowly to the glassware. Since a greateramount of heat is supplied .at the ends ofthe shield, the shield is'adapted to radiatemore heat at the ends thereof. Another advantage ofthis construction is that the shield covers the unit and prevents smallfragments of glass from falling on the heating units. Molten glass is anelectrical conductor. Hence, particles of glass accumulating on theheating units tend to cause short circuits, reducing the life" of theunits.

As illustrated in Fig. 5, the above heating effect may be attained byutilizing a heating unit having a uniform heating capacity throughoutits length and extending a shield 2! over the central or middle portionof the unit, I The shield prevents direct radiation of heat at thecentral portion and causes a substantial amount of heat to be conveyedby convection around the ends of the shield to the sides of the lehr,thereby increasing the heat delivered to the sides of the tunnel.

In Fig. 6, a. heating unit is shown in'operation in a lehr tunnel 22orthe like having a conveyor belt.24, or other suitable support, for theware to be annealed. Any of the units illustrated in Figs. 1 tot may beutilized, since they are all designed to produce more heat at the sidesof Hence, the operation of the heating unit about to be described is.applicable to all the embodiments illustrated herein.

Preferably, the units, when used in connection with glass annealinglehrs or the like, are positioned at various points along the length ofthe lehr to produce a desired temperature gradient. When current passesthrough the resistance strip to cause radiation of heat, the heatingcurrents,

- illustrated herein by the arrows, rise upwardly at the sides of thetunnel. This is due to the greatest -heating intensity being at the endsof the unit, whereby stronger currents are created gle with the heatcurrents rising "upwardly at the middle of the unit. Any drafts or otheradverse cooling currents at the sides of thetunnel are heated to thedesired temperature of the tunnel and the heating currents in turn areslightly cooled to approximately the same temperature as the currentsrising upwards at the middle of the heating unit; Hence, when the sideand middle currents meet, they merge at substantially the sametemperature to provide a uniform heating atmosphere for annealing theglassware.

In this manner, the effective heat supplied to the glassware is uniformthroughout the width of the tunnel and the ware is properly annealed,regardless of its position on the conveyor with respect to the sides ofthe lehr. By balancing the heat, adverse air currents within the lehrare minimized and desired temperature can be maintained more accurately.This permits better annealing and prevents breakage of the ware.

- It will be seen that the present invention provides an improvedheating unit for lehrs and the like which is simple in construction,easy to manufacture, and readily removed and replaced. The

unit has a greater heat-intensity at the ends than at the middle tocreate heating currents of different intensities adapted to mingletogether and produce a uniform heating medium transversely of the lehr.The heating units are rugged in construction and can readily withstandany rough usage to which they may be subjected.

As various changes may be made in the form. construction and arrangementof the parts herein without departing from the spirit and scope of theinvention and without sacrificing any of its advantages, it is to beunderstood that all matter herein is to be interpreted as illustrativeand not in a limiting sense.

Having thus described my invention, I claim:

1. A heating unit for an electric lehr, comprising a supportingstructure adapted to be mounted in the lehr, a resistance element formedof a strip of material bent into a series of loops and mounted upon saidsupporting structure and positioned thereon to radiate heat in avertical direction, the loops of said strip at the ends of the heatingunit being adapted to produce more heat per unit of length of theheating unit than the loops at the middle thereof, and a shield mountedon the supporting structure and extending over said resistance element,said shield distributing more heat at its end portions than at themiddle thereof.

2. A heating unit of the class described, comprising a supporting frame,a resistance element for producing heat mounted upon said supportingframe, said resistance strip having portions adapted to produce moreheat at the ends of the frame per unit of length of the frame than atthe middle of the frame, and a shield mounted on said supportingstructure and extending over said resistance element, said shielddistributing more heat at its end portions than at the equal middleportions thereof.

3. A heating unit of the class described, comprising a supportingstructure, a resistance element mounted on said supporting structurehaving a series of connected groups of heating portions spacedlengthwise along said structure, the portions at the ends of saidelement being adapted to produce more heat than portions at the middleof said element, and a shield having a top portion extending over atleast the .middle of said resistance element and having flanges attachedto said supporting structure.

4. A heating unit for an electric lehr comprising a supporting structureadapted to be mounted in the lehr, a resistance element formed of astrip of material bent into a series of loops and mounted upon saidsupporting structure, said resistance element having a greater number ofloops per unit of length at the ends of said supporting structure thanat the middle thereof to produce more heat at the ends of said structurethan at the middle and a shield encasing said resistance element andmounted on said supporting structure.

5. A heating unit of the class described, comprising a resistance stripformed into a series of loops, means for holding said loops outofcontact with each other, said'resistance strip having at least twice thenumber of loops per unit of length at the ends of said means than at thecen- 'ter thereof to produce at least twice as much heat at the endsthereof and a shield formed of a heat conducting metal extending oversaid resistance strip.

6. In a heating unit of the class described, the combination of asupporting frame, an integral strip of resistance material mounted onsaid frame bent into groups of relatively short loops extendinglengthwise of said frame, a plurality of the groups at each end of saidframe having a greater heating capacity than an equal number of groupsat the middle of the frame to produce more heat at the ends of saidframe, and a shield having a top portion extending over said loops andhaving depending side portions attached to said supporting frame.

Louise. Pmzzonr, Ju. f

